May 11, 2012
Our apologies for the absence of recent posts to the cannon blog. Historic Trades’ attention has been focused on the Armoury project and a host of smaller undertakings around town, but a group of folks has been working diligently behind the scenes to get ready for another pour.
After our failed pour of June 2010, the Historic Trades brickmasons removed the entire superstructure of the furnace down to the melting pan. Examining the mass of bronze there did not reveal anything conclusive about the failure, but reinforced the probability that the metal simply was not hot enough when we tapped the furnace. Based on that, the founders, gunsmiths, and masons made some changes in the furnace design, and beginning last autumn, the masons rebuilt the furnace accordingly. The new design also incorporates a wooden shed, built by the Historic Trades carpenters. This shed will cover the kiln to protect it from the weather on an everyday basis, provide some protection for the furnace should it rain during the firing process, and t better support the hoisting gear with which the molds and castings are handled.
Cutting up the hunk of bronze left in the furnace so that we could reuse it was more difficult than expected. After a couple unsuccessful attempts, rescue came in the form of Newport News Shipbuilding. Several of their employees picked up the mass, hauled it to Newport News, used some of their specialized equipment to cut it up, and returned it to us in pieces that we can set directly into the furnace.
While all this was going on, the founders and gunsmiths completed another set of light three-pounder molds. Their experiments with new loam mixtures led to much more satisfactory results than in the past. When they removed the core and burned out the wax, they ended up with sharp, clean interiors, and the molds seem to be more sturdy than earlier ones. They will take the molds over to the College of William and Mary on May 7, where Professor Mike Jabbur will fire them to a “redware” hardness and ensure that they are completely dry.
So, we are ready to try again. With some extremely helpful advice and hands-on assistance from Andrew Eshelman and Stephan Williams of Newport News Shipbuilding, we are planning to pour on Thursday, May 24. We will be preheating the furnace much longer than in the past, and will be using a modern pyrometer to monitor heating more accurately and better understand how the furnace is operating.
The proposed schedule — all weather dependent, of course — from now until then is:
May 7: Load molds in ceramic kiln at the College of William and Mary
May 9: Pick up molds
May 14: Test fire furnace
May 21: Load bronze in furnace and start preheating
May 22: Continue to raise furnace temperature
May 23: Continue firing. Bury mold
May 24: Build tapping channel. Bring bronze to pouring temperature. Pour.
May 25: Excavate mold and open
From May 21 until pouring, this will be a round-the-clock operation. As before, it all will be happening adjacent to the parking lot across from the Visitor Center and adjacent to Great Hopes Plantation.
This project is possible through a generous gift by the Ambrose and Ida Fredrickson Foundation. Research assistance was provided by Firepower: The Royal Artillery Museum, and the National Park Service. We are grateful to the Museum Restoration Service and The Royal Artillery Historical Trust for the use of their images.